1 00:00:08,310 --> 00:00:13,590 This is one of multiple videos where I discuss net or network address translation. 2 00:00:13,980 --> 00:00:20,970 In this video, I'm answering a question from Pedro, who's attending my June three Q&A course. 3 00:00:25,840 --> 00:00:28,300 This is the inside global address. 4 00:00:28,330 --> 00:00:32,380 In other words, this is the netted address of that PC. 5 00:00:32,890 --> 00:00:38,650 This is the address of that PC when traffic is sent onto the internet. 6 00:00:39,100 --> 00:00:44,020 So let's do a telnet to 8.828.1. 7 00:00:45,110 --> 00:00:48,230 Let's configure the server for telnet. 8 00:00:51,800 --> 00:00:54,110 At the moment it's got transport input. 9 00:00:54,110 --> 00:00:54,860 None. 10 00:00:55,010 --> 00:00:57,950 So I'm gonna say transport input Telnet. 11 00:00:58,850 --> 00:01:01,070 Back on router three. 12 00:01:01,370 --> 00:01:05,450 Can we telnet to 82822821? 13 00:01:05,510 --> 00:01:06,590 Yes, we can. 14 00:01:06,800 --> 00:01:08,570 And we're on right one. 15 00:01:09,350 --> 00:01:12,950 Now can we ping 82822822. 16 00:01:13,730 --> 00:01:14,930 No, we can't. 17 00:01:17,460 --> 00:01:19,890 Can we ping 8282823? 18 00:01:19,920 --> 00:01:20,890 No, we can't. 19 00:01:20,910 --> 00:01:22,560 Those addresses don't exist. 20 00:01:23,490 --> 00:01:24,810 So at the moment. 21 00:01:26,610 --> 00:01:29,250 We've got one net translation. 22 00:01:29,250 --> 00:01:30,090 This one. 23 00:01:30,930 --> 00:01:41,750 What I'll do now is create another one for the real IP address of the host inside local ten. 24 00:01:41,760 --> 00:01:41,880 Two. 25 00:01:41,880 --> 00:01:43,230 One, two, two, two. 26 00:01:43,990 --> 00:01:57,070 And we'll set the global IP address to 8.8 to 8.2 and make that extendable IP net inside source. 27 00:01:57,790 --> 00:01:59,770 Let's do the same for 3 to 3. 28 00:02:01,290 --> 00:02:03,000 And added to that address. 29 00:02:03,000 --> 00:02:05,310 So show IP. 30 00:02:06,030 --> 00:02:12,930 Net translation we have three net entries in the net table. 31 00:02:13,110 --> 00:02:19,200 At the moment, there are no outside local outside global entries because no traffic is being initiated 32 00:02:19,200 --> 00:02:22,170 by the PC to those servers. 33 00:02:23,510 --> 00:02:30,290 But if we now ping this address, which didn't work in the past, it now works. 34 00:02:30,470 --> 00:02:33,770 And the same is true for 82822823. 35 00:02:34,010 --> 00:02:36,860 So we're getting some ICMP echoes there. 36 00:02:37,790 --> 00:02:39,200 Let's call that. 37 00:02:39,290 --> 00:02:43,190 So 828823 works and or two works. 38 00:02:44,160 --> 00:02:50,550 And if you look at the net translations, we can see the ICMP translations in the table here. 39 00:02:50,830 --> 00:02:54,240 ICMP may be a little bit more difficult to read. 40 00:02:55,500 --> 00:02:58,110 So let me do a telnet. 41 00:02:58,800 --> 00:03:02,430 So telnet it from this PC to the server. 42 00:03:03,570 --> 00:03:07,770 And notice we can see that the destination port is 23. 43 00:03:08,520 --> 00:03:12,510 So support from the PC is a random port number. 44 00:03:13,050 --> 00:03:18,450 So this is the net translation for the telnet session. 45 00:03:19,410 --> 00:03:22,710 Debug IP net if I hit enter here. 46 00:03:23,700 --> 00:03:25,400 We should see translations. 47 00:03:25,410 --> 00:03:26,340 There we go. 48 00:03:26,910 --> 00:03:29,280 And then I'll just type some characters. 49 00:03:30,470 --> 00:03:33,080 Notice we're getting natural translations. 50 00:03:34,420 --> 00:03:44,170 A source of 82822824 going to 8228281 means that the destination address is translated to 10.1 to 1.1, 51 00:03:44,440 --> 00:03:49,060 and then it's translated back for the reverse traffic. 52 00:03:52,260 --> 00:03:52,590 Okay. 53 00:03:52,590 --> 00:03:56,490 So in summary, show run pipe include net. 54 00:03:57,820 --> 00:04:04,030 To set up a network such as this where you have multiple internal servers and you want them to be accessible 55 00:04:04,030 --> 00:04:05,200 from the Internet. 56 00:04:05,380 --> 00:04:13,060 One way to set this up is to create an individual static net entry per server. 57 00:04:13,760 --> 00:04:17,089 This is the real IP address configured on the device. 58 00:04:17,360 --> 00:04:21,170 In other words, that's the address that's being configured on the device. 59 00:04:21,170 --> 00:04:23,690 It's called the inside local address. 60 00:04:23,990 --> 00:04:26,510 This is the inside global address. 61 00:04:26,600 --> 00:04:33,530 This is the netted or virtual IP address associated with this physical IP address configured on the 62 00:04:33,530 --> 00:04:34,310 device. 63 00:04:34,670 --> 00:04:37,250 So Pedro, I'm hoping that answers your question. 64 00:04:37,580 --> 00:04:40,340 I also hope that this helps everyone else. 65 00:04:40,430 --> 00:04:45,620 If you enjoyed this video, please like it and please subscribe to my YouTube channel. 66 00:04:45,800 --> 00:04:47,570 I wish you all the very best.